Refining of shale oil



5, 1952 J. R. SMlTH ETAL 2,606,143

REFINING OF SHALE OIL Filed Aug. 31, 1950 4 /24 3 3 T Desorbeht recovery :32 C: I Desorbent storage /25 4 l 4 T 3O Stripping 4 29 27 unit Desorption recovery 28 5T Nitrogen extract Air storage [F E t uen recover 23 6 y Crude shale 8 A 1e storage 7 OtI- exl uent mu m 1 A l PSeparation stage 5 E 9 y Eluent V 7 I storage 22 Q F 1 M Stripping I un't ,21 i is n T Hydrocarbon J product v Y storage INVENTORS' James R. Smith ATTORNEY Patented Aug. 5, 1 952 R name or SHALE on. James R. Smith and Gerald U. Dinneen, Laramie,

, I Wy0., assignors as represented by to the United States of America the Secretary of the Interior I Application August 21, 1950, Serial No. 182,528" I 9 Claims. (01.196-14'7) (Granted under the act of amended April 30, 1928;

The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This inventionrelates to the refining of crude oils derived from oil shale-and is particularly concerned with a method for the removal of or-. ganic nitrogen compounds from shale oils wherein these compounds normally occur in large amounts.

- The term shale oil, as commonly used in the United States, andas employed herein, refers to a mixture of hydrocarbons and certain nitrogen, sulfur, and oxygen compounds obtained usually by destructive distillation of sedimentary rocks containing kerogen, commonly termed oil shales. Deposits of oil shale of varying extent and richness are found in this country, and in many parts of the world. Of the domestic deposits, the richest known are those foundin the so-called Green River formation situated principally in Colorado, Wyoming, and Utah. i 1

In the handling and refining of crude shale oil one of the main problems encountered has been the occurrence of large percentages of organic nitrogen compounds in the crude disti11ate.

A typical crude prepared from Colorado shale, for example, although containing only from 1 to 2%v nitrogen by weight, will. contain in .some of the higher boiling fractions from 30 to 50% of nitrogen compounds. These nitrogen compounds, which are largely heterocyclics, seriously effect the stability of any type of fuel that may be made from the crude and therefore must be removed to produce a commercially acceptable product. During refining, nitrogen compounds is a serious disadvantage since the shale oil 'nitrogen'compounds act" as, poisons to catalytic cracking catalysts and thus prevent the application of the catalytic cracking techniquejfor the conversion of'the heavy crudes into lighter diesel and gasoline fractions. The presence of large amou'nts'of nitrogen compounds furthermore gives the oil an extremely dark color andrenders analysis of the crudes very difficult.

' Several methods have been previously proposed for removal of these nitrogencompounds. For example, it is possible to effect their removal, from various fractions of the crude by acid treatment but this method results in a loss of from 20 to 40 in the acid sludge. High pressure hydrothe presence of these genation of the crude at from 6000 to 10,000 lbs.

per square inch has also been proposed, but this method requires the iusejofv expensive hydrogen and complicated high pressure equipment.

March 3, use s 370 0.6.757)

According to the present invention a method has been discoveredfor removing the organic nitrogen compounds present :in shale oil by a relatively simple adsorption technique by which it is possible to make'a clean cut separation between the hydrocarbons and the substantial amounts of nitrogen compounds present in the crude; By means of the method of the invention, the shale oil is separated into tWo' separate fractions, one containingsubstantially all the hydrocarbons present-in the -crude oil, including the paraffins, naphthenes,-olefins, and aromatics, and the other fraction containing substantially all the nitrogen compounds present. The invention is based upon the discovery that, in contrast to other adsorbent materials, an adsorbent comprised essentially of magnesium silicate will strongly adsorb the type of nitrogen compounds found in shale oil, while at the same time will have substantially noafiinity for the type of hydrocarbons, including the high percentage of olefins an'd aromatics, found in crude shale distillates. The high selectivity and the large adsorbent capacitypf magnesium silicate adsorbents permits a substantially quantitative removal of nitrogen compounds which are present in amounts ranging from 10 to by weight depending on the fraction under consideration. Further advantages of a magnesium silicate adsorbent is the ease with which the. large amounts.

of adsorbed nitrogen compounds may be removed from the adsorbent and recovered withsubstantially no loss, and the easewithfwhich the adsorbent may be regenerated for further use. Other known adsorbents; commonly used in the petroleum industry and for other purposes, such as silica gel, alumina, fullers earth, activated bauxite and activated carbon are unsuited for the removal of nitrogen compoundsin the amounts in1 which they are present in" most crude shale 01s..

Broadly the method of the invention involves contacting. theflsh'ale oil, containing substantial amounts ornitrog'en'compounds, with an adsorbent comprised, essentiallyofmag'nesium silicate, the contacting being accomplished preferably by percolating the nitrogen] containing shale oil through a tower containing the adsorbent, to thereby adsorb the major portion. of the organic nitrogen compounds on the magnesium silicate. The nonadsorbed portionofj the shale oil, consisting essentially of'hydrocarbons, is then recovered, most, desirably'bywashing the adsorbent with an, essentially nonpolar eluting. agent which'causes' ,substantially,-no desorption of nitrogen compounds. Following the recovery of the hydrocarbons, the nitrogen compounds may be separately recovered by contacting the adsorbent with a polar desorbing agent which is more strongly adsorbed than the nitrogen compounds,

4 i are solids, or very viscous at room temperature were diluted with n-pentane to prevent solidification of the material in the adsorbent.

In each case, after the sample had entered the and which thus causes substantially complete dis- 5 adsorbent,.n-.pentane was'added at thetop of the placement of the nitrogen compounds from the column, allowedto percolate therethrough, and adsorbent. After removal of the desorbing agent the penta and the portion f the sample eluted and after regeneration by steaming and drying, from the adsorbent were collected in areceiver as for example, the magnesium silicate adsorbent is they eme d r m t e o u e a o ready for reuse. 4 a pentane-through the column was continued until I the composition of the material issuing from the Examples bottom of the-column approached closely to that 4; v, of purep'entane as indicated by the refractive The follow n a p illustratethe applicaindex thereof. Approximately two liters of pention of the invention to the separation andsepa- =-t per '100 grams of sample w r required t rate recovery of the nitrogen and hydrocarbon giye complete 1 t1 compounds present i several c ud 'd ti a- Following the entane elution a fresh receiver tion fractions of increas g ie lil i a was introduced under the column and methanol increasin p rcen age of nitrogencompoun s. was then introduced atthe to of the column In each case. the crude shale oil from which the a d an wed to percolate down through the addistillation fraction. was \preparedrwas produced b t Th metha l, b in m r strongly y the so-called N-T-U retortingproc ss fr madsorbed on the magnesium silicate than the Colorado oil shale yielding "an avera of; 3 alnitrogen compounds, idisplac'edthe nitrogen "comlons of crude oiljper ton of shale. According to pounds d th w r ll t d i th fre h the N-T-U process, a cylindrical :retortjs. fi d. receiver at the bottom .ofthe column. Percolawith crushed shale. The shalerat the top of the. tion of methanol through the column was conretort is i nited and air is; blown :downwardly tinned.untilsubstantially pure methanol issued through the bed of'jshale. Hea furnished by from the bottom or the column, approximately combustion of the upper lay r 'oisha s r es t 1.2 liters of methanol being required for the de-r decompose'kerogen' in the layers of shale beneath sorption of 100 gramsoi' sample. the combustionz ne- 'I;heoi1 vapors which dis- The pentane eluted fraction, containing the till from the shale are carried out Of the retort bulk of the hydrocarbons with small amounts of in the hot air stream. The combustion zone adnitrogen. compounds, and the methanoldesorbed vances downwardly through the complete charge fraction, containing substantially all the nitroin the cylindrical retort, residual carbon in the gen compounds present in the original sample, shale from which the oil has 'alreadybeen driven were then stripped respectively of pentane and supporting combustion and furnishing heat methanol and the composition-of each fraction throughout the retorting process. Distillation determined. temperatures are in the; neighborhood of from In the table below are (tabulated the results 850 to 1000 F. From this crude, four distilla- 4 obtained by the procedure outlined above,-giving tion fractions were preparedza naphtha fraction the percent of nitrogen andithe percent of nitroboiling between 155-415? F., a-kerosene fraction gen compounds in the original sample, in the penboiling between 400-585: F., a light gas oil fractane eluted fraction, and in the methanol detion boiling between 570 750 Fr, andaiheavy gas sorbed fraction, respectively.

I Nitrogen F Nitrogen Nitrogen I Nitrogen We. ages. start lliiziitit 5 93 ample ofcompouuds cenfin sample cent m tame eluted cent in pencentmmethcentinmeth- 1n sample Sample inaction tans elutedv anoldesorbed anoldesorbed fXBCtlOD. V traction fraction 1 Heavy gas oil boiling over w 625F .-;s2o 1.78 40.8 0:11 2.5. .3. 13 85.4 2 "Light gas oil boiling range. i I I 570750 F 280 r 1. 82 36:4' 0.1a 2:0 as; so. a 3 Kerosine boiling range 400,- i i i z 585 F 20o, 1.41 .20. 2- 0.11 1.5 5.05 72.5 4 Naphtha boiling range 155- g oil fraction boiling above 625 F.

A weighed sample of each of the four fractions mentioned above was allowed to percolate down through a column packed with a granulated magnesium silicate adsorbent. Theadsorbent used was prepared generally according to the process described in U. S. Patent 2,393,625 toSimons, except that the activation ste described in this patent, accomplished by drying th'efprecipitated' magnesium silicate gel at an elevated temperature up to 1300 F., was omitted, the "precipitated gel merely being air dried. This adsorbent was employed in a particle size of from 30 to mesh; and was packed in a column having a height to diameter ratio of about 40. The weight of adsorbent employed in each case was equal to 300 times the weight of nitrogen in the sample. The heavy gas oil and the light gas oil fractions which suitable physical prop j It will be note'dthat in each 'ca'se'wll over'90 percent of the nitrogen com oundstn the original sample are concentrateddn the methanol desorbed fraction. -Further analysis of the nitrogen high fra'ction indicated "thepresence'of approximately 4 to 7 percent sulfur compounds and "also some oxygen-containing heteroc'yclic's, little if anyhydrocarbons being present. .The pentane eluted fractio ,"on theother hand, "contained a small percentageof nitrogen compounds, from 4 to 7 percent sulfur compounds, the bulk of this fraction being hydrocarbons, including paraflins, naphthenes, olefins, and aromatics.

The magnesiuml'silicate adsorbent employed ispreferably a synthetica'llyprepared precipitated magnesium silicategel although any synthetic or natural magnesium silicate having ertie's 1(e. g. hardness and porosity) maybe employed. The hydrated gel, after precipitation, may be activated, if desired, by rapid drying at an elevated temperature, but preferably the hydrated precipitated gel is not subjected to an activating treatment but is merely air dried. Although activation by rapid drying at an elevated temperature increases the adsorption capacity of the gel for nitrogen compounds, the activation causes an even greater increase in its adsorption capacity for some nonnitrogencontaining compounds, such as! naphthalene and its homologs and other condensed ring aromatic hydrocarbons, in certain shale oil fractions. Consequently, for more clean cut separations, an unactivated air dried mag' nesium silicate adsorbent is employed. 1 v

The ratio of adsorbent to the shale oil being treated necessary to provide eflicient separation of the nitrogen compounds and hydrocarbons will vary somewhat according to the mannerof preparation of the magnesium silicate adsorbent and with the type of shale oil fraction being processed. In general, an amount by weight of magnesium silicate adsorbent equal to from 300 to 500 times the weight of nitrogen in the shale oil to be processed is required.

After desorption of the nitrogen compounds, and elimination of the bulk of the desorbent by sweeping with a hot gas for example, the adsorbent 'willusually retain a'certain amount of impurities consisting chiefly of an unidentified type of nitrogen compound and possibly oxygen compounds. To regenerate the adsorbent for reuse it is not necessary or desirable to burn ofi these impurities. A steam purge at a temperature between 290 and 310 F. followed by air drying will ordinarily suflice to render the adsorbent fit for reuse.

The method of the invention may be carried out according to any of the usual adsorption techniques but is preferably conducted according to the so-called percolation filtration technique in which the shale oil to be processed is added to the top of a tower packed with the adsorbent and allowed to percolate down through the adsorbent, the nonadsorbed material being collected at the bottom of the column. This technique lends itself readily to the elution' and desorption'steps, the eluting and desorbing agents likewise being,

tower to remove the nonadsorbed hydrocarbons and the adsorbed nitrogen compounds respec-' tively. Since decreasing the particle size of the adsorbent usually will increase its adsorption capacity but will decrease the percolation rate, in the application of the percolation technique, an adsorbent particle size should be chosen which ofiers a satisfactory compromise between these two factors. On the basis of these. considerations, particle sizes ranging from to lOO'mesh may be satisfactorily employed. The ratio of height to diameter of the packed column'is preferably at least 30 but may range between 12 and 150.

As eluting agents for washing the nonadsorbed hydrocarbon portion of the shale oil from the magnesium silicate adsorbent, any. essentially nonpolar organic solvent which causes substantially no desorption of the nitrogen compounds from the adsorbent may be employed. The most satisfactory eluents are saturated hydrocarbons,'-

lthe paraffin series. Aro not desirable.

particularly those of matics and olefins are, in general,

since they ;are more strongly adsorbed on the magnesium silicate. adsorbentfand consequentlypercolated down through the cause greater-desorption of nitrogen compounds. The eluent should have a boiling range such that it can be easily stripped by distillation from the eluted shale oil hydrocarbons. Thus, depending on the boiling range of the shale oil fraction, theeluentmay have a boiling range as high as 250 to 300 F. However, eluents having a boiling range in the vicinity of 100 F. are more generally suitable. Examples of particular satisfactory eluents are the normal or iso-pentanes, hexanes, heptanes, and octanes, or any mixture of these,'such as a saturated petroleum out having a boiling range in the vicinity of the boiling range of these compounds.

As desorbing agents for desorbing the nitrogen compounds from the magnesium silicates adsorb-' ent, organic solvents which are miscible with the nitrogen compounds in the shale oil, which have distinctly polar properties and which effect substantially complete displacement of nitrogen compounds from the adsorbent may be employed. It is essential or course, be'more strongly adsorbed on the magnesium silicate adsorbent than the nitrogen compounds present in shale oil. The desorbent should have a boiling range below about 300 F. so that it can be easily handled and easily stripped from the desorbed nitrogen compounds. Low boiling alcohols, particularly the aliphatic alcohols, such as methyl, ethyl,- n-propyl and'iso-propyl are examples of particularly suitable desorbents.

The method of the invention is applicable to all types of shale oil which contain appreciable amounts of organic nitrogen compounds and is particularly useful in respect to shale oils which contain over 10% by weight of nitrogen compounds because of the difficulties inherent in the separation and'separat'e recovery of these compounds in suchlarge amounts when in intimate admixture with hydrocarbons of similar structure. The type-and the amount of nitrogen compounds present in a particular shale oil will vary somewhat-according to the type of oilshale from which it was produced, the method of retorting, and the type of refining operation, if any, to which it has been subjected. lower boiling shale oil fractionscontain a smaller percentage of nitrogen and of nitrogen com pounds than the higher boiling fractions. The invention has particular application to the type of shale oils derived by destructive distillation at temperatures from 700 to 1500'F. from oil shales found in the 'so-called Green River formation situated principallyin Colorado, Wyoming, and Utah, which contain nitrogen compounds in amounts ranging from 5% in the lightest fractions of the crude to as high as in the heavy fractions.

If desired, the method of the invention may be carried out strictly as a batch operation. However, when operating on a large scale it is preferable to maintain continuous charge and product flows in the operation of the percolation towers. Reference is now made to the accompanying drawing which diagrammatically illustrates the operation of the invention in this manner.

In the drawing, eleven adsorption towers are shown, bearing the reference'numerals l to II, respectively, although more orfewer maybe employed. The process illustrated involves 5 stages, each stage involving the use of one or more towers; In the first stage (towers l-I I), separation of the nitrogen compounds from the hy-' drocarbons is accomplished 'by adsorption ofthe nitrogen compounds on the magnesium silicate thatthe desorbing agent In general, the

7 adsorbent followed by elution of the hydrocarbon compounds; in the second stage (tower 6) residual eluent is recovered by sweeping a stream of heated gas through the tower; in the third stage (towers 4 and 5) the nitrogen compounds are desorbed; in the fourth stage (tower 3) residual desorbent is removed by sweeping with a hot gas; and in the'fifth stage (towers l and 2) the adsorbent is regenerated for reuse. The towers are transferred successively from one stage to another in the direction and order indicated by the arrows at the right of each adsorption column. After-regeneration, the regenerated tower re-enters'the process as the last tower in the separation stage. Asshown in the drawing, for example, after regeneration, tower No. I will take over the functions of-tower ll; tow'er II will take over the functions of tower l; tower III will take over the functions of tower 9, and so forth. By a suitable system of manifolding and valve arrangement, shiftingof the towers successively through the "various stages of the process can be accomplished in such a manner that continuous charge and product flows are maintained.

As shown in the drawing, a shale oil fraction, which has notbeen processed for the removal of nitrogen compounds, is fed from storage tank l2 by line 13 into mixing tank I4 where it is mixed, if desired, with eluent from eluent storage tank l5. ,The oil-eluent mixture is fed by line l6 into theseparation stage, flowing into tower 9 and percolating downwardly through towers 9, l0, and II where the nitrogen compounds are removed. from the mixture by the magnesium silicate adsorbent. In towers 1 and 8 fresh eluent is supplied from eluent storage tank 15 by line I! and percolates downwardly through these towers, to remove the hydrocarbons from adsorbent which has been previously saturated to'capacity with nitrogen compounds. The eluent-hydrocarbon mixture flowing from the bottom of tower 8 is percolated through the remaining towers of the separation stage and the total eluent-hydrocarbon mixture from the separation stage is withdrawn from the last tower thereof by line I8 and conducted to a stripping unit I 9. In the stripping unit I9, which may be, for example, a distillation column of suitable design, the hydrocarbon products are stripped of eluent and conducted by line 20 tohydrocarbon product storage tank 2|, the eluent being conducted by line 22 to eluent storage tank I 5.

In tower 6, the adsorbent, saturated with nitrogen compounds, but washed free of hydrocarbons, is stripped of residual eluent by a stream of heated air or other gas. The eluent, after being recovered from the gas stream in a suitable recovery unit 23 is then conducted to eluent storage I5.

' In towers 4 and nitrogen compounds are removed from the adsorbent by a suitable desorbing agent introduced fromstorage tank 24 by line 25. Desorbed nitrogen compounds and desorbent are conducted by line 28 to a suitable stripping unit 21 where the nitrogen compounds are separated from the desorbent and conducted by line 28 to storage tank 29. The desorbent is conducted to desorbent storage tank 24 by line 30 for reuse.

In tower 3 the residual desorbent remaining after desorption of the nitrogen compounds is stripped from the adsorbent by a stream of l1eat ed air. The air stream, containing desorbent is conducted toa recovery unit 3| where the desorbent is recovered and conducted to storage by line 32. l 1 r ascen s In tower 2,- theadsorbent, previously stripped of desorbent, is regenerated by steam purging at a temperature of from 290 to 310 F. After drying in tower l the adsorbent is then ready to be returned to the process.

It is to be understood, of course, that when tower 9 becomes saturated to capacity with nitrogen compounds, the flow of oil charge to this tower is cut off, and by provision of the necessary piping connections (not shown) and by suitable shifting of valves, the fiow of raw charge is transferred to tower l8; tower 9 taking over the functions of tower 8, tower 8 taking over the functions of tower 7, and so forth, each tower changing its functions as previously explained.

The hydrocarbons recovered and stored in tank 2| are virtually free of nitrogen compounds and may be processed according to conventional petroleum techniques, including catalytic cracking techniques. The nitrogen-containing fraction, stored in tank 29 may be processed separately, for the removal of nitrogen compounds, for example, by high pressure hydrogenation, or put to any other desired use.

It is to be understood that the above description, together with the specific examples and embodiments described, is intended merely to illustrate the invention, and that the invention is not to be limited thereto, nor in any way except by the scope of the appended claims.

We claim:

1. A method for the separation of organic nitrogen compounds from shale oils containing said nitrogen compounds in amounts ranging from about 10% to 60% by weight and likewise containing substantial amounts of olefinic and aromatic hydrocarbons comprising the steps of contacting said shale oil with an adsorbent comprising magnesium silicate, adsorbing the major portion of said nitrogen compounds on said magnesium silicate adsorbent, and recovering the nonadsorbed portion of said shale oil.

2. A method for the separation of organic nitrogen compounds from shale oil containing said nitrogen compounds in amounts ranging from about 10% to 60% by weight and likewise containing substantial amounts of oleflnic and aromatic hydrocarbons tacting said shale oil with an adsorbent comprising magnesium silicate, adsorbing the major portion of said nitrogen compounds on said magnesium silicate adsorbent, and recovering the nonadsorbed portion of said shale oil by washing said adsorbent with an essentially nonpolar eluting agent causing substantially no desorption of saidnitrogen compounds.

3. A method for theseparation of organic nitrogen compounds from shale oils containing said nitrogen compounds in amounts ranging from about 10% to 60% by weight and likewise containing substantial amounts of olefinic and aromatic hydrocarbons comprising the steps of contacting said shale oil with an adsorbent comprising magnesium silicate, adsorbing the major portion of said nitrogen compounds on said magnesium silicate adsorbent, and recovering the nonadsorbed portion of said shale oil by washing said adsorbent with comprising a saturated hydrocarbon.

4. A method for separately recovering hydrocarbons and organic nitrogen compounds from a shaleoil containing said nitrogen compounds in amounts ranging from weight and likewise containing substantial amounts or oleflnic and comprising the steps of con a nonpolar eluting agent about 10% to 60% by aromatic hydrocarbons comprising the steps of contacting said shale oil with an adsorbent comprising magnesium silicate, adsorbing the major portion of said nitrogen compounds on said magnesium silicate adsorbent, separately recovering the hydrocarbons present in said shale oil by washing said adsorbent with an essentially nonpolar eluting agent causing substantially no desorption of said nitrogen compounds, and then separately recovering said nitrogen compounds by contacting said adsorbent with a polar desorbing agent causing substantially complete displacement of said nitrogen compounds from said adsorbent.

5. A method for separately recovering hydrocarbons and organic nitrogen compounds from a shale oil containing said nitrogen compounds in amounts ranging from about to 60% by weight and likewise containing substantial amounts of olefinic and aromatic hydrocarbons comprising the steps of contacting said shale oil with an adsorbent comprising magnesium silicate, adsorbing the major portion of said nitrogen compounds on said magnesium silicate adsorbent, separately recovering the hydrocarbons present in said shale oil by washing said adsorbent with an essentially nonpolar eluting agent comprising a saturated hydrocarbon, and then separately recovering said nitrogen compounds by contacting said adsorbent with a polar desorbing agent comprising an aliphatic alcohol.

6. A method for the separation of organic nitrogen compounds from shale oil containing said nitrogen compounds in amounts ranging from about 10% to 60% by weight and likewise containing substantial amounts of olefinic and aromatic hydrocarbons, comprising the steps of percolating said shale oil through a granular magnesium silicate adsorbent to thereby adsorb the major portion of said nitrogen compounds on said magnesium silicate adsorbent, and recovering the nonadsorbed portion of said shale oil by percolating an essentially nonpolar eluting agent through said adsorbent thereby to wash said nonadsorbed portion therefrom while causing substantially no desorption of said nitrogen compounds.

'7. A method according to claim 5 wherein the nonpolar eluting agent comprises a saturated hydrocarbon.

8. A method for separately recovering hydrocarbons and organic nitrogen compounds from a shale oil containing said nitrogen compounds in amounts ranging from about 10% to by weight and likewise containing substantial amounts of olefinic and aromatic hydrocarbons comprising the steps of percolating said shale oil through a granular magnesium silicate adsorbent to thereby adsorb the major portion of said nitrogen compounds on said magnesium silicate adsorbent, separately recovering the hydrocarbons present in said shale oil by percolating an essentially nonpolar eluting agent through said adsorbent thereby to wash said hydrocarbons therefrom while causing substantially no desorption of said nitrogen compounds, and then separately recovering said nitrogen compounds by percolating a polar desorbing agent through said adsorbent thereby causing substantially complete displacement of said nitrogen compounds from said adsorbent.

9. A method for separately recovering hydrocarbons and organic nitrogen compounds from a shale oil containing said nitrogen compounds in amounts ranging from about 10% to 60% by weight and likewise containing substantial amounts of olefinic and aromatic hydrocarbons comprising the steps of percolating said shale oil through a granular magnesium silicate adsorbent to thereby adsorb the major portion of said nitrogen compounds on said magnesium silicate adsorbent, separately recovering the hydrocarbons present in said shale oil by percolating an essentially nonpolar eluting agent comprising a saturated hydrocarbon through said adsorbent, and then separately recovering said nitrogen compounds by percolating a polar desorbing agent comprising an alphatic alcohol through said adsorbent.

JAMES R. SMITH. GERALD U. DINNEEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,384,315 Kuhl Sept. 4, 1945 2,402,804 Chechot June 25, 1946 OTHER REFERENCES 

1. A METHOD FOR THE SEPARATION OF ORGANIC NITROGEN COMPOUNDS FROM SHALE OILS CONTAINING SAID NITROGEN COMPOUNDS IN AMOUNTS RANGING FROM ABOUT 10% TO 60% BY WEIGHT AND LIKEWISE CONTAINING SUBSTANTIAL AMOUNTS OF OLEFINIC AND AROMATIC HYDROCARBONS COMPRISING THE STEPS OF CONTACTING SAID SHALE OIL WITH AN ADSORBENT COMPRISING MAGNESIUM SILICATE, ADSORBING THE MAJOR PORTION OF SAID NITROGEN COMPOUNDS ON SAID MAGNESIUM SILICATE ADSORBENT, AND RECOVERING THE NONADSORBED PORTION OF SAID SHALE OIL 